Physical Science: Forces, Motion, and Energy
What this domain tests
A force is a push or a pull. Know that forces can be balanced, producing no change in motion, or unbalanced, causing a change in speed or direction. Understand friction as a force that opposes motion, and gravity as a force pulling objects toward Earth. Know that an object at rest stays at rest and a moving object keeps moving unless a force acts on it.
Energy
Energy is the ability to do work and comes in forms such as motion, light, sound, heat, and stored energy. Energy can transfer from one object to another and change form, but it is not created or destroyed. Know simple machines such as levers, pulleys, and inclined planes, which make work easier by changing the direction or size of a force.
Traps to watch for
Questions often say a moving object has no force on it when it is simply moving at constant speed, or claim energy disappears when it is used. Another trap is confusing speed with force, or assuming heavier objects always fall faster in air-free conditions. Watch for answers that ignore friction.
Rule of thumb
Ask "what forces act, and are they balanced?" Balanced forces mean no change in motion; unbalanced forces mean acceleration. For example, a book resting on a table has gravity pulling down and the table pushing up equally, so it stays still.